Sensory devices based on amplified fluorescence quenching of solid-state conjugated polymer films can be highly sensitive, due to the amplification that arises from delocalized excitons sampling many potential binding sites within one excited state lifetime. Previous work has demonstrated highly sensitive detection schemes using these amplifying fluorescent polymers for a number of analytes in solution and vapor phase, as described in U.S. Publication No. 2003/0178607. For example, sensors for the ultratrace detection of high explosives such as 2,4,6-trinitrotoluene (TNT) have been shown to display high sensitivity comparable to that of trained canines. In many cases, the transduction mechanism is photoinduced charge transfer (PICT) from a polymer donor to a substantially planar, aromatic analyte that can bind to the conjugated polymer via pi-stacking interactions. For example, TNT is a planar, nitroaromatic molecule that can readily form a pi-complex with a conjugated polymer.
Although planar and/or aromatic compounds are often present in many explosives, present day security is in need of systems capable of matching comprehensive detection of a broader range of high explosives and toxins. For example, many military explosives compositions contain 2,4,6-hexahydro-1,3,5-triazinane (RDX) and/or pentaerythritol tetranitrate (PETN), both of which are non-planar, non-aromatic, explosive compounds.
Accordingly improved methods are needed.